Cotton variety MX0623B2RF

ABSTRACT

The invention relates to the novel cotton variety designated MX0623B2RF. Provided by the invention are the seeds, plants, plant parts and derivatives of the cotton variety MX0623B2RF. Also provided by the invention are tissue cultures of the cotton variety MX0623B2RF and the plants regenerated therefrom. Still further provided by the invention are methods for producing cotton plants by crossing the cotton variety MX0623B2RF with itself or another cotton variety and plants produced by such methods.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of cotton breeding.In particular, the invention relates to the novel cotton varietyMX0623B2RF.

2. Description of Related Art

There are numerous steps in the development of any novel, desirableplant germplasm. Plant breeding begins with the analysis and definitionof problems and weaknesses of the current germplasm, the establishmentof program goals, and the definition of specific breeding objectives.The next step is selection of germplasm that possess the traits to meetthe program goals. The goal is to combine in a single variety animproved combination of desirable traits from the parental germplasm.These important traits may include resistance to diseases and insects,tolerance to drought and heat, tolerance to herbicides, improvements infiber traits and numerous other agronomic traits that may be desirableto the farmer or end user.

Choice of breeding or selection methods depends on the mode of plantreproduction, the heritability of the trait(s) being improved, and thetype of variety used commercially (e.g., F₁ hybrid variety, purelinevariety, etc.). For highly heritable traits, a choice of superiorindividual plants evaluated at a single location will be effective,whereas for traits with low heritability, selection should be based onmean values obtained from replicated evaluations of families of relatedplants. Popular selection methods commonly include pedigree selection,modified pedigree selection, mass selection, recurrent selection andbackcrossing.

The complexity of inheritance influences choice of the breeding method.Backcross breeding is used to transfer one or a few favorable genes fora highly heritable trait into a desirable variety. This approach hasbeen used extensively for breeding disease-resistant plant varieties.Various recurrent selection techniques are used to improvequantitatively inherited traits controlled by numerous genes. The use ofrecurrent selection in self-pollinating crops depends on the ease ofpollination, the frequency of successful hybrids from each pollination,and the number of offspring from each successful cross.

Each breeding program should include a periodic, objective evaluation ofthe efficiency of the breeding procedure. Evaluation criteria varydepending on the goal and objectives, but should include gain fromselection per year based on comparisons to an appropriate standard,overall value of the advanced breeding lines, and number of successfulvarieties produced per unit of input (e.g., per year, per dollarexpended, etc.).

Promising advanced breeding lines are thoroughly tested and compared toappropriate standards in environments representative of the commercialtarget area(s) for generally three or more years. The best lines arecandidates for new commercial varieties. Those still deficient in a fewtraits may be used as parents to produce new populations for furtherselection.

These processes, which lead to the final step of marketing anddistribution, may take as much as eight to 12 years from the time thefirst cross is made. Therefore, development of new varieties is atime-consuming process that requires precise forward planning, efficientuse of resources, and a minimum of changes in direction.

A most difficult task is the identification of individuals that aregenetically superior, because for most traits the true genotypic valueis masked by other confounding plant traits or environmental factors.One method of identifying a superior plant is to observe its performancerelative to other experimental plants and to one or more widely grownstandard varieties. Single observations are generally inconclusive,while replicated observations provide a better estimate of geneticworth.

The goal of plant breeding is to develop new, unique and superior cottonvarieties. The breeder initially selects and crosses two or moreparental lines, followed by repeated selfing and selection, producingmany new genetic combinations. Each year, the plant breeder selects thegermplasm to advance to the next generation. This germplasm is grownunder unique and different geographical, climatic and soil conditions,and further selections are then made, during and at the end of thegrowing season. The varieties which are developed are unpredictable.This unpredictability is because the breeder's selection occurs inunique environments, with no control at the DNA level (usingconventional breeding procedures), and with millions of differentpossible genetic combinations being generated. A breeder of ordinaryskill in the art cannot predict the final resulting lines he develops,except possibly in a very gross and general fashion. The same breedercannot produce the same variety twice by using the exact same originalparents and the same selection techniques. This unpredictability resultsin the expenditure of large amounts of research monies to developsuperior new cotton varieties.

Pureline cultivars, such as generally used in cotton and many othercrops, are commonly bred by hybridization of two or more parentsfollowed by selection. The complexity of inheritance, the breedingobjectives and the available resources influence the breeding method.The development of new varieties requires development and selection, thecrossing of varieties and selection of progeny from superior crosses.

Pedigree breeding and recurrent selection breeding methods are used todevelop varieties from breeding populations. Breeding programs combinedesirable traits from two or more varieties or various broad-basedsources into breeding pools from which varieties are developed byselfing and selection of desired phenotypes. The new varieties areevaluated to determine which have commercial potential.

Pedigree breeding is commonly used for the improvement ofself-pollinating crops. Two parents which possess favorable,complementary traits are crossed to produce an F₁. An F₂ population isproduced by selfing one or several F₁ plants. Selection of the bestindividuals may begin in the F₂ population or later depending uponobjectives of the breeder; then, beginning in the F₃, the bestindividuals in the best families can be selected. Replicated testing offamilies can begin in the F₃ or F₄ generation to improve theeffectiveness of selection for traits with low heritability. At anadvanced stage of inbreeding (i.e., F₆ and F₇), the best lines ormixtures of phenotypically similar lines are typically tested forpotential release as new varieties.

Mass and recurrent selections can be used to improve populations ofeither self- or cross-pollinating crops. A genetically variablepopulation of heterozygous individuals is either identified or createdby intercrossing several different parents. The best plants are selectedbased on individual superiority, outstanding progeny, or excellentcombining ability. The selected plants are intercrossed to produce a newpopulation in which further cycles of selection are continued.

The single-seed descent procedure in the strict sense refers to plantinga segregating population, harvesting a sample of one seed per plant, andusing the one-seed sample to plant the next generation. When thepopulation has been advanced from the F₂ to the desired level ofinbreeding, the plants from which lines are derived will each trace todifferent F₂ individuals. The number of plants in a population declineseach generation due to failure of some seeds to germinate or some plantsto produce at least one seed. As a result, not all of the F₂ plantsoriginally sampled in the population will be represented by a progenywhen generation advance is completed.

The modified single seed descent procedures involve harvesting multipleseed (i.e., a single lock or a simple boll) from each plant in apopulation and combining them to form a bulk. Part of the bulk is usedto plant the next generation and part is put in reserve. This procedurehas been used to save labor at harvest and to maintain adequate seedquantities of the population. The multiple-seed procedure may be used tosave labor. It is considerably faster to gin bolls with a machine thanto remove one seed by hand for the single-seed procedure. Themultiple-seed procedure also makes it possible to plant the same numberof seeds of a population each generation of inbreeding. Enough seeds areharvested to make up for those plants that did not germinate or produceseed.

Descriptions of other breeding methods that are commonly used fordifferent traits and crops can be found in one of several referencebooks (e.g., Allard, 1960; Simmonds, 1979; Sneep et al., 1979; Fehr,1987a,b).

Proper testing should detect any major faults and establish the level ofsuperiority or improvement over current varieties. In addition toshowing superior performance, there must be a demand for a new varietythat is compatible with industry standards or which creates a newmarket. The introduction of a new variety will incur additional costs tothe seed producer, the grower, processor and consumer; for specialadvertising and marketing, altered seed and commercial productionpractices, and new product utilization. The testing preceding release ofa new variety should take into consideration research and developmentcosts as well as technical superiority of the final variety. Forseed-propagated varieties, it must be feasible to produce seed easilyand economically.

The two cotton species commercially grown in the United States areGossypium hirsutum, commonly known as short staple or upland cotton andGossypium barbadense, commonly known as extra long staple (ELS) or, inthe United States, as Pima cotton. Upland cotton fiber is used in a widearray of coarser spin count products. Pima cotton is used in finer spincount yarns (50-80) which are primarily used in more expensive garments.Other properties of Pima cotton are critical because of fiber end use.

Cotton is an important and valuable field crop. Thus, a continuing goalof plant breeders is to develop stable, high yielding cotton varietiesthat are agronomically sound. The reasons for this goal are obviously tomaximize the amount and quality of the fiber produced on the land usedand to supply fiber, oil and food for animals and humans. To accomplishthis goal, the cotton breeder must select and develop plants that havethe traits that result in superior cultivars.

The goal of a commercial cotton breeding program is to develop new,unique and superior cotton varieties. In cotton, important traitsinclude higher fiber (lint) yield, earlier maturity, improved fiberquality, resistance to diseases and insects, tolerance to drought andheat, and improved agronomic traits. The breeder initially selects andcrosses two or more parental lines, followed by generation advancementand selection, thus producing many new genetic combinations. The breedercan theoretically generate billions of different genetic combinationsvia this procedure.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to seed of the cottonvariety MX0623B2RF. The invention also relates to plants produced bygrowing the seed of the cotton variety MX0623B2RF, as well as thederivatives of such plants. As used herein, the term “plant” includesplant cells, plant protoplasts, plant cells of a tissue culture fromwhich cotton plants can be regenerated, plant calli, plant clumps, andplant cells that are intact in plants or parts of plants, such aspollen, flowers, seeds, bolls, leaves, stems, and the like.

Another aspect of the invention relates to a tissue culture ofregenerable cells of the cotton variety MX0623B2RF, as well as plantsregenerated therefrom, wherein the regenerated cotton plant expressesall the physiological and morphological characteristics of a plant grownfrom the cotton seed designated MX0623B2RF.

Yet another aspect of the current invention is a cotton plant of thecotton variety MX0623B2RF comprising at least a first transgene, whereinthe cotton plant is otherwise capable of expressing all thephysiological and morphological characteristics of the cotton varietyMX0623B2RF. In particular embodiments of the invention, a plant isprovided that comprises a single locus conversion. A single locusconversion may comprise a transgenic gene which has been introduced bygenetic transformation into the cotton variety MX0623B2RF or aprogenitor thereof. A transgenic or non-transgenic single locusconversion can also be introduced by backcrossing, as is well known inthe art. In certain embodiments of the invention, the single locusconversion may comprise a dominant or recessive allele. The locusconversion may confer potentially any desired trait upon the plant asdescribed herein.

Still yet another aspect of the invention relates to a first generation(F₁) hybrid cotton seed produced by crossing a plant of the cottonvariety MX0623B2RF to a second cotton plant. Also included in theinvention are the F₁ hybrid cotton plants grown from the hybrid seedproduced by crossing the cotton variety MX0623B2RF to a second cottonplant. Still further included in the invention are the seeds of an F₁hybrid plant produced with the cotton variety MX0623B2RF as one parent,the second generation (F₂) hybrid cotton plant grown from the seed ofthe F₁ hybrid plant, and the seeds of the F₂ hybrid plant.

Still yet another aspect of the invention is a method of producingcotton seeds comprising crossing a plant of the cotton varietyMX0623B2RF to any second cotton plant, including itself or another plantof the variety MX0623B2RF. In particular embodiments of the invention,the method of crossing comprises the steps of a) planting seeds of thecotton variety MX0623B2RF; b) cultivating cotton plants resulting fromsaid seeds until said plants bear flowers; c) allowing fertilization ofthe flowers of said plants; and, d) harvesting seeds produced from saidplants.

Still yet another aspect of the invention is a method of producinghybrid cotton seeds comprising crossing the cotton variety MX0623B2RF toa second, distinct cotton plant which is nonisogenic to the cottonvariety MX0623B2RF. In particular embodiments of the invention, thecrossing comprises the steps of a) planting seeds of cotton varietyMX0623B2RF and a second, distinct cotton plant, b) cultivating thecotton plants grown from the seeds until the plants bear flowers; c)cross pollinating a flower on one of the two plants with the pollen ofthe other plant, and d) harvesting the seeds resulting from the crosspollinating.

Still yet another aspect of the invention is a method for developing acotton plant in a cotton breeding program comprising: obtaining a cottonplant, or its parts, of the variety MX0623B2RF; and b) employing saidplant or parts as a source of breeding material using plant breedingtechniques. In the method, the plant breeding techniques may be selectedfrom the group consisting of recurrent selection, mass selection, bulkselection, backcrossing, pedigree breeding, genetic marker-assistedselection and genetic transformation. In certain embodiments of theinvention, the cotton plant of variety MX0623B2RF is used as the male orfemale parent.

Still yet another aspect of the invention is a method of producing acotton plant derived from the cotton variety MX0623B2RF, the methodcomprising the steps of: (a) preparing a progeny plant derived fromcotton variety MX0623B2RF by crossing a plant of the cotton varietyMX0623B2RF with a second cotton plant; and (b) crossing the progenyplant with itself or a second plant to produce a progeny plant of asubsequent generation which is derived from a plant of the cottonvariety MX0623B2RF. In one embodiment of the invention, the methodfurther comprises: (c) crossing the progeny plant of a subsequentgeneration with itself or a second plant; and (d) repeating steps (b)and (c) for at least 2-10 additional generations to produce an inbredcotton plant derived from the cotton variety MX0623B2RF. Also providedby the invention is a plant produced by this and the other methods ofthe invention. Plant variety MX0623B2RF-derived plants produced by thisand the other methods of the invention described herein may, in certainembodiments of the invention, be further defined as comprising thetraits of plant variety MX0623B2RF given in Table 1.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.”

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating specific embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides, in one aspect, methods and composition relatingto plants, seeds and derivatives of the cotton variety MX0623B2RF. Thecotton variety MX0623B2RF has been judged to be uniform for breedingpurposes and testing. The variety can be reproduced by planting andgrowing seeds of the variety under self-pollinating or sib-pollinatingconditions, as is known to those of skill in the agricultural arts.Variety MX0623B2RF shows no variants other than what would normally beexpected due to environment or that would occur for almost anycharacteristic during the course of repeated sexual reproduction.

Variety MX0623B2RF is an insect-protected and herbicide-tolerant cottonvariety, as a result of containing event MON 15985 and event MON 88913.Event MON 15985 produces Cry1Ac and Cry2Ab proteins, which are Bacillusthuringensis (subspecies kurstaki) proteins that protect plants fromfeeding damage caused by lepidopteran insect pests. Event MON 88913produces a 5-enolpyruvyshikimate-3-phosphate synthase protein fromAgrobacterium sp. Strain CP4 (CP4 EPSPS), which confers tolerance toglyphosate, the active ingredient in the ROUNDUP® family of agriculturalherbicides.

The results of an objective description of the variety are presentedbelow, in Table 1. Those of skill in the art will recognize that theseare typical values that may vary due to environment and that othervalues that are substantially equivalent are within the scope of theinvention.

TABLE 1 Phenotypic Description of Variety MX0623B2RF CHARACTERISTICVARIETY MX0623B2RF 1. Species G. hirsutum L. 2. Areas of AdaptationEastern Adapted Plains Adapted Delta Adapted Western Adapted CentralAdapted Arizona Adapted Blacklands Adapted 3. General Plant HabitSpreading Foliage Intermediate Stem Lodging Erect Fruiting Branch NormalGrowth Intermediate Leaf Color Medium Green Boll Shape Length > widthBoll Breadth Broadest at middle 4. Maturity Medium Full 5. Plant Cm to1^(st) Fruiting Branch: (from 16.0 cotyledonary node) No. of Nodes to1^(st) Fruiting Branch: 6.1 (excluding cotyledonary node) Mature PlantHeight cm: (from 115.4 cotyledonary node to terminal) 6. Leaf TypeNormal Pubescence Sparse Nectaries Present 7. Stem PubescenceIntermediate 8. Glands Leaf Normal Stem Normal Calyx Lobe: (normal isabsent) Normal 9. Flower Petals Cream Pollen Cream Petal Spot Absent 10.Seed Seed Index: (g/100 seeds, fuzzy 8.080 basis) Lint Index: (glint/100 seeds) 7.04 11. Boll Lint Percent Picked 45.60 Number of Seedsper Boll 33.33 Grams Seed Cotton per Boll 5.11 Number of Locules perBoll 4.4 Boll Type Open 12. Fiber Properties Length: (inches, 2.5% SL)1.095 Uniformity: (%) 82.404 Strength, T1 (g/tex) 27.07 Elongation, E1(%) 5.21 Micronaire 4.55 13. Nematodes, Insects and Pests Root-KnotNematode Susceptible Boll Weevil Susceptible Bollworm Resistant CottonAphid Susceptible Cotton Fleahopper Susceptible Cotton LeafwormResistant Cutworm Susceptible Fall Armyworm Resistant Reniform nematodeSusceptible Grasshopper Susceptible Lygus Susceptible Pink BollwormResistant Spider mite Susceptible Stink bug Susceptible ThripsSusceptible Tobacco Bud Worm Resistant These are typical values. Valuesmay vary due to environment. Other values that are substantiallyequivalent are within the scope of the invention.

The performance characteristics of cotton variety MX0623B2RF were alsoanalyzed and comparisons were made with competing varieties. The resultsof the analysis are presented below, in Tables 2-3.

TABLE 2 Performance Data for Variety MX0623B2RF Trait MX0623B2RFDP164B2RF Lint Percentage 45.60 41.58 Fiber Length 1.095 1.126 FiberUniformity 82.404 83.592 Fiber Strength 27.07 30.21 Fiber Elongation5.21 6.78 Micronaire 4.55 4.73

TABLE 3 Further Performance Data for Variety MX0623B2RF Pedigree TSCYDLP LTAC MIC LNTH UNIF SFC STR EL PHY 485 WRF 3349.0 41.62 1390.2 4.791.122 84.225 9.00 29.81 6.62 MX0623B2RF 2909.8 45.60 1327.0 4.55 1.09582.404 10.37 27.07 5.21 ST 4554B2RF 3186.0 41.58 1324.3 4.73 1.12683.592 9.02 30.21 6.78 DP 164 B2RF 3085.7 40.53 1248.4 4.57 1.169 83.0359.51 29.20 5.56 Overall Mean 3048.1 41.66 1268.5 4.54 1.127 83.428 9.5028.98 6.02 # Locs 24 24 24 24 24 24 24 24 24 # Reps 96 46 96 47 47 47 4747 47 CV 9.889 2.617 10.320 4.704 1.912 0.965 6.076 3.815 3.866 LSD(.05)170.806 0.618 74.176 0.121 0.012 0.456 0.327 0.627 0.132 F-Statistic7.823 67.729 10.931 18.004 37.451 21.941 22.672 44.930 75.570 P-Value0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Repeatability0.872 0.985 0.909 0.944 0.973 0.954 0.956 0.978 0.987 Root MSE 301.4331.090 130.903 0.214 0.021 0.805 0.578 1.106 0.233

I. BREEDING COTTON VARIETY MX0623B2RF

One aspect of the current invention concerns methods for crossing thecotton variety MX0623B2RF with itself or a second plant and the seedsand plants produced by such methods. These methods can be used forpropagation of the cotton variety MX0623B2RF, or can be used to producehybrid cotton seeds and the plants grown therefrom. A hybrid plant canbe used as a recurrent parent at any given stage in a backcrossingprotocol during the production of a single locus conversion of thecotton variety MX0623B2RF.

The variety of the present invention is well suited to the developmentof new varieties based on the elite nature of the genetic background ofthe variety. In selecting a second plant to cross with MX0623B2RF forthe purpose of developing novel cotton varieties, it will typically bedesired to choose those plants which themselves exhibit one or moreselected desirable characteristics. Examples of potentially desiredcharacteristics include higher fiber (lint) yield, earlier maturity,improved fiber quality, resistance to diseases and insects, tolerance todrought and heat, and improved agronomic traits.

Any time the cotton variety MX0623B2RF is crossed with another,different, variety, first generation (F₁) cotton progeny are produced.The hybrid progeny are produced regardless of characteristics of the twovarieties produced. As such, an F₁ hybrid cotton plant may be producedby crossing MX0623B2RF with any second cotton plant. The second cottonplant may be genetically homogeneous (e.g., inbred) or may itself be ahybrid. Therefore, any F₁ hybrid cotton plant produced by crossingcotton variety MX0623B2RF with a second cotton plant is a part of thepresent invention.

Cotton plants can be crossed by either natural or mechanical techniques.Natural pollination occurs in cotton either by self pollination ornatural cross pollination, which typically is aided by pollinatingorganisms. In either natural or artificial crosses, flowering andflowering time are important considerations.

The cotton flower is perfect in that the male and female structures arein the same flower. The crossed or hybrid seed can be produced by manualcrosses between selected parents. Floral buds of the parent that is tobe the female can be emasculated prior to the opening of the flower bymanual removal of the male anthers. At flowering, the pollen fromflowers of the parent plants designated as male, can be manually placedon the stigma of the previous emasculated flower. Seed developed fromthe cross is known as first generation (F₁) hybrid seed. Planting ofthis seed produces F₁ hybrid plants of which half their geneticcomponent is from the female parent and half from the male parent.Segregation of genes begins at meiosis thus producing second generation(F₂) seed. Assuming multiple genetic differences between the originalparents, each F₂ seed has a unique combination of genes.

Self-pollination occurs naturally in cotton with no manipulation of theflowers. For the crossing of two cotton plants, it is typicallypreferable to utilize artificial hybridization. In artificialhybridization, the flower used as a female in a cross is manually crosspollinated prior to maturation of pollen from the flower, therebypreventing self fertilization, or alternatively, the male parts of theflower are emasculated using a technique known in the art. Techniquesfor emasculating the male parts of a cotton flower include, for example,physical removal of the male parts, use of a genetic factor conferringmale sterility, and application of a chemical gametocide to the maleparts.

For artificial hybridization employing emasculation, flowers that areexpected to open the following day are selected on the female parent.The buds are swollen and the corolla is just visible through the calyxor has begun to emerge. Usually no more than two buds on a parent plantare prepared, and all self-pollinated flowers or immature buds areremoved with forceps. Special care is required to remove immature budsthat are hidden under the stipules at the leaf axil, and could developinto flowers at a later date. The flower is grasped between the thumband index finger and the location of the stigma determined by examiningthe sepals. The calyx is removed by grasping a sepal with the forceps,pulling it down and around the flower, and repeating the procedure untilthe five sepals are removed. The exposed corolla is removed with care toavoid injuring the stigma. Cross-pollination can then be carried outusing, for example, petri dishes or envelopes in which male flowers havebeen collected. Desiccators containing calcium chloride crystals can beused in some environments to dry male flowers to obtain adequate pollenshed.

Either with or without emasculation of the female flower, handpollination can be carried out by removing the stamens and pistil with aforceps from a flower of the male parent and gently brushing the anthersagainst the stigma of the female flower. Access to the stamens can beachieved by removing the front sepal and keel petals, or piercing thekeel with closed forceps and allowing them to open to push the petalsaway. Brushing the anthers on the stigma causes them to rupture, and thehighest percentage of successful crosses is obtained when pollen isclearly visible on the stigma. Pollen shed can be checked by tapping theanthers before brushing the stigma. Several male flowers may have to beused to obtain suitable pollen shed when conditions are unfavorable, orthe same male may be used to pollinate several flowers with good pollenshed.

Cross-pollination is more common within rows than between adjacent rows;therefore, it may be preferable to grow populations with genetic malesterility on a square grid to create rows in all directions. Forexample, single-plant hills on 50-cm centers may be used, withsubdivision of the area into blocks of an equal number of hills forharvest from bulks of an equal amount of seed from male-sterile plantsin each block to enhance random pollination.

II. IMPROVEMENT OF COTTON VARIETIES

In certain further aspects, the invention provides plants modified toinclude at least a first desired trait. Such plants may, in oneembodiment, be developed by a plant breeding technique calledbackcrossing, wherein essentially all of the desired morphological andphysiological characteristics of a variety are recovered in addition toa genetic locus transferred into the hybrid via the backcrossingtechnique. The term backcrossing as used herein refers to the repeatedcrossing of a hybrid progeny back to a starting variety into whichintroduction of the desired trait is being carried out. The parentalplant which contributes the locus or loci for the desired trait istermed the nonrecurrent or donor parent. This terminology refers to thefact that the nonrecurrent parent is used one time in the backcrossprotocol and therefore does not recur.

The parental cotton plant to which the locus or loci from thenonrecurrent parent are transferred is known as the recurrent parent asit is used for several rounds in the backcrossing protocol (Poehlman etal., 1995; Fehr, 1987; Sprague and Dudley, 1988). In a typical backcrossprotocol, the original line of interest (recurrent parent) is crossed toa second variety (nonrecurrent parent) that carries the genetic locus tobe transferred. The resulting progeny from this cross are then crossedagain to the recurrent parent and the process is repeated until a cottonplant is obtained wherein essentially all of the desired morphologicaland physiological characteristics of the recurrent parent are recoveredin the converted plant, in addition to the transferred locus from thenonrecurrent parent.

The backcross process may be accelerated by the use of genetic markers,such as Simple Sequence Length Polymorphisms (SSLPs) (Williams et al.,1990), Randomly Amplified Polymorphic DNAs (RAPDs), DNA AmplificationFingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs),Arbitrary Primed Polymerase Chain Reaction (AP-PCR), Amplified FragmentLength Polymorphisms (AFLPs) (EP 534 858, specifically incorporatedherein by reference in its entirety), and Single NucleotidePolymorphisms (SNPs) (Wang et al., 1998) to identify plants with thegreatest genetic complement from the recurrent parent.

The selection of a suitable recurrent parent is an important step for asuccessful backcrossing procedure. The goal of a backcross protocol isto add or substitute one or more new traits in a variety. To accomplishthis, a genetic locus of the recurrent parent is modified or substitutedwith the desired locus from the nonrecurrent parent, while retainingessentially all of the rest of the desired genetic, and therefore thedesired physiological and morphological constitution of the originalplant. The choice of the particular nonrecurrent parent will depend onthe purpose of the backcross; one of the major purposes is to add somecommercially desirable, agronomically important trait to the plant. Theexact backcrossing protocol will depend on the characteristic or traitbeing altered to determine an appropriate testing protocol. Althoughbackcrossing methods are simplified when the characteristic beingtransferred is a dominant allele, a recessive allele may also betransferred. In this instance it may be necessary to introduce a test ofthe progeny to determine if the desired characteristic has beensuccessfully transferred.

Many traits have been identified that are not regularly selected for inthe development of a new variety but that can be improved bybackcrossing techniques. A genetic locus conferring the traits may ormay not be transgenic. Examples of such traits known to those of skillin the art include, but are not limited to, male sterility, herbicidetolerance, resistance for bacterial, fungal, or viral disease, insectresistance, male fertility, enhanced nutritional quality and improvedfiber characteristics. These genes are generally inherited through thenucleus, but may be inherited through the cytoplasm.

Direct selection may be applied where a genetic locus acts as a dominanttrait. An example of a dominant trait is the herbicide tolerance trait.For this selection process, the progeny of the initial cross are sprayedwith the herbicide prior to the backcrossing. The spraying eliminatesany plants which do not have the desired herbicide tolerancecharacteristic, and only those plants which have the herbicide tolerancegene are used in the subsequent backcross. This process is then repeatedfor all additional backcross generations.

Many useful traits are those which are introduced by genetictransformation techniques. Methods for the genetic transformation ofcotton are known to those of skill in the art. For example, broadlyapplicable plant transformation methods which have been describedinclude Agrobacterium-mediated transformation, microprojectilebombardment, electroporation, and direct DNA uptake by protoplasts.

Agrobacterium-mediated transfer is a widely applicable system forintroducing gene loci into plant cells, including cotton. An advantageof the technique is that DNA can be introduced into whole plant tissues,thereby bypassing the need for regeneration of an intact plant from aprotoplast. Modern Agrobacterium transformation vectors are capable ofreplication in E. coli as well as Agrobacterium, allowing for convenientmanipulations (Klee et al., 1985). Moreover, recent technologicaladvances in vectors for Agrobacterium-mediated gene transfer haveimproved the arrangement of genes and restriction sites in the vectorsto facilitate the construction of vectors capable of expressing variouspolypeptide coding genes. The vectors described have convenientmulti-linker regions flanked by a promoter and a polyadenylation sitefor direct expression of inserted polypeptide coding genes.Additionally, Agrobacterium containing both armed and disarmed Ti genescan be used for transformation.

In those plant strains where Agrobacterium-mediated transformation isefficient, it is the method of choice because of the facile and definednature of the gene locus transfer. The use of Agrobacterium-mediatedplant integrating vectors to introduce DNA into plant cells is wellknown in the art (Fraley et al., 1985; U.S. Pat. No. 5,563,055). Oneefficient means for transformation of cotton in particular istransformation and regeneration of cotton hypocotyl explants followinginoculation with Agrobacterium tumefaciens from primary callusdevelopment, embryogenesis, embryogenic callus identification,transgenic cotton shoot production and the development of transgenicplants, as is known in the art.

To effect transformation by electroporation, for example, one may employeither friable tissues, such as a suspension culture of cells orembryogenic callus or alternatively one may transform immature embryosor other organized tissue directly. In this technique, one wouldpartially degrade the cell walls of the chosen cells by exposing them topectin-degrading enzymes (pectolyases) or mechanically wound tissues ina controlled manner. Protoplasts may also be employed forelectroporation transformation of plants (Bates, 1994; Lazzeri, 1995).For example, the generation of transgenic cotyledon-derived protoplastswas described by Dhir and Widholm in Intl. Patent Appl. Publ. No. WO92/17598, the disclosure of which is specifically incorporated herein byreference. When protoplasts are used, transformation can also beachieved using methods based on calcium phosphate precipitation,polyethylene glycol treatment, and combinations of these treatments(see, e.g., Potrykus et al., 1985; Omirulleh et al., 1993; Fromm et al.,1986; Uchimiya et al., 1986; Marcotte et al., 1988).

Microprojectile bombardment is another efficient method for deliveringtransforming DNA segments to plant cells. In this method, particles arecoated with nucleic acids and delivered into cells by a propellingforce. Exemplary particles include those comprised of tungsten,platinum, and preferably, gold. For the bombardment, cells in suspensionare concentrated on filters or solid culture medium. Alternatively,immature embryos or other target cells may be arranged on solid culturemedium. The cells to be bombarded are positioned at an appropriatedistance below the macroprojectile stopping plate.

Microprojectile bombardment techniques are widely applicable, and may beused to transform virtually any plant species. The application ofmicroprojectile bombardment for the transformation of cotton isdescribed, for example, in Rajasekaran et al., 1996. An illustrativeembodiment of a method for microprojectile bombardment is the BiolisticsParticle Delivery System, which can be used to propel particles coatedwith DNA or cells through a screen, such as a stainless steel or Nytexscreen, onto a surface covered with target cells. The screen dispersesthe particles so that they are not delivered to the recipient cells inlarge aggregates. It is believed that a screen intervening between theprojectile apparatus and the cells to be bombarded reduces the size ofprojectiles aggregate and may contribute to a higher frequency oftransformation by reducing the damage inflicted on the recipient cellsby projectiles that are too large.

It is understood to those of skill in the art that a locus of transgenicorigin need not be directly transformed into a plant, as techniques forthe production of stably transformed cotton plants that pass single locito progeny by Mendelian inheritance is well known in the art. Suchsingle loci may therefore be passed from parent plant to progeny plantsby standard plant breeding techniques that are well known in the art.Non-limiting examples of traits that may be introduced directly or bybackcrossing are presented below.

A. Male Sterility

Male sterility genes can increase the efficiency with which hybrids aremade, in that they eliminate the need to physically emasculate the plantused as a female in a given cross. Where one desires to employmale-sterility systems, it may be beneficial to also utilize one or moremale-fertility restorer genes. For example, where cytoplasmic malesterility (CMS) is used, hybrid crossing requires three inbred lines:(1) a cytoplasmically male-sterile line having a CMS cytoplasm; (2) afertile inbred with normal cytoplasm, which is isogenic with the CMSline for nuclear genes (“maintainer line”); and (3) a distinct, fertileinbred with normal cytoplasm, carrying a fertility restoring gene(“restorer” line). The CMS line is propagated by pollination with themaintainer line, with all of the progeny being male sterile, as the CMScytoplasm is derived from the female parent. These male sterile plantscan then be efficiently employed as the female parent in hybrid crosseswith the restorer line, without the need for physical emasculation ofthe male reproductive parts of the female parent.

The presence of a male-fertility restorer gene results in the productionof fully fertile F₁ hybrid progeny. If no restorer gene is present inthe male parent, male-sterile hybrids are obtained. Examples ofmale-sterility genes and corresponding restorers which could be employedwith the plants of the invention are well known to those of skill in theart of plant breeding. Examples of such genes include CMS-D2-2 (Meyer,1975), CMS-hir, CMS-D8 (Stewart, 1992), CMS-D4 (Meshram et al., 1994),and CMS-C1 (Zhang and Stewart, 1999). Fertility can be restored toCMS-D2-2 by the D2 restorer in which the restorer factor(s) wasintroduced from the genome of G. harknessii Brandegee (D2-2).Microsporogenesis in both CMS systems aborts during the premeiotic stage(Black, 1997). One dominant restorer gene from the D8 restorer wasidentified to restore fertility of CMS-D8 (Zhang and Stewart, 2001). TheD2 restorer for CMS-D2-2 also restores the fertility of CMS-D8, CMS-hir,and CMS-C1 (Zhang and Stewart, 1999).

B. Herbicide Tolerance

Numerous herbicide tolerance genes are known and may be employed withthe plants of the invention. An example is a gene conferring toleranceto a herbicide that inhibits the growing point or meristem, such asimidazalinone or sulfonylurea. Exemplary genes in this category code formutant ALS and AHAS enzymes as described, for example, by Lee et al.,(1988); Gleen et al., (1992); Miki et al., (1990).

Tolerance genes for glyphosate (tolerance conferred by mutant5-enolpyruvl-3 phosphikimate synthase (EPSPS and aroA genes) and otherphosphono compounds such as glufosinate (phosphinothricin acetyltransferase (PAT) and Streptomyces hygroscopicus phosphinothricin-acetyltransferase (bar) genes) may also be used. For example, U.S. Pat. No.4,940,835 to Shah, et al., discloses the nucleotide sequence of a formof EPSPS which can confer glyphosate tolerance. A DNA molecule encodinga mutant aroA gene can be obtained under ATCC accession number 39256,and the nucleotide sequence of the mutant gene is disclosed in U.S. Pat.No. 4,769,061 to Comai. European patent application No. 0 333 033 toKumada et al., and U.S. Pat. No. 4,975,374 to Goodman et al., disclosenucleotide sequences of glutamine synthetase genes which confertolerance to herbicides such as L-phosphinothricin. The nucleotidesequence of a phosphinothricin-acetyltransferase gene is provided inEuropean application No. 0 242 246 to Leemans et al. DeGreef et al.,(1989), describe the production of transgenic plants that expresschimeric bar genes coding for phosphinothricin acetyl transferaseactivity. Exemplary genes conferring tolerance to herbicidal phenoxypropionic acids and cycloshexones, such as sethoxydim and haloxyfop arethe Acct-S1, Accl-S2 and Acct-S3 genes described by Marshall et al.,(1992). U.S. Patent Application No: 20030135879 describes isolation of agene for dicamba monooxygenase (DMO) from Psueodmonas maltophilia whichis involved in the conversion of a herbicidal form of the herbicidedicamba to a non-toxic 3,6-dichlorosalicylic acid and thus may be usedfor producing plants tolerant to this herbicide.

Genes are also known conferring tolerance to a herbicide that inhibitsphotosynthesis, such as triazine (psbA and gs+ genes) and benzonitrile(nitrilase gene). Przibilla et al., (1991), describe the transformationof Chlamydomonas with plasmids encoding mutant psbA genes. Nucleotidesequences for nitrilase genes are disclosed in U.S. Pat. No. 4,810,648to Stalker, and DNA molecules containing these genes are available underATCC Accession Nos. 53435, 67441, and 67442. Cloning and expression ofDNA coding for a glutathione S-transferase is described by Hayes et al.,(1992).

C. Disease Resistance

Plant defenses are often activated by specific interaction between theproduct of a disease resistance gene (R) in the plant and the product ofa corresponding avirulence (Avr) gene in the pathogen. A plant line canbe transformed with cloned resistance gene to engineer plants that areresistant to specific pathogen strains. See, for example Jones et al.,(1994) (cloning of the tomato Cf-9 gene for resistance to Cladosporiumfulvum); Martin et al., (1993) (tomato Pto gene for resistance toPseudomonas syringae pv.); Mindrinos et al., (1994) (Arabidopsis RPS2gene for resistance to Pseudomonas syringae). Logemann et al., (1992),for example, disclose transgenic plants expressing a barleyribosome-inactivating gene have an increased resistance to fungaldisease.

A viral-invasive protein or a complex toxin derived therefrom may alsobe used for viral disease resistance. For example, the accumulation ofviral coat proteins in transformed plant cells imparts resistance toviral infection and/or disease development effected by the virus fromwhich the coat protein gene is derived, as well as by related viruses.See Beachy et al., (1990). Coat protein-mediated resistance has beenconferred upon transformed plants against alfalfa mosaic virus, cucumbermosaic virus, tobacco streak virus, potato virus X, potato virus Y,tobacco etch virus, tobacco rattle virus and tobacco mosaic virus.

A virus-specific antibody may also be used. See, for example,Tavladoraki et al., (1993), who show that transgenic plants expressingrecombinant antibody genes are protected from virus attack.

D. Insect Resistance

One example of an insect resistance gene includes a Bacillusthuringiensis protein, a derivative thereof, or a synthetic polypeptidemodeled thereon. See, for example, Geiser et al., (1986), who disclosethe cloning and nucleotide sequence of a Bt δ-endotoxin gene. Moreover,DNA molecules encoding 6-endotoxin genes can be purchased from theAmerican Type Culture Collection, Manassas, Va., for example, under ATCCAccession Nos. 40098, 67136, 31995 and 31998. Another example is alectin. See, for example, Van Damme et al., (1994), who disclose thenucleotide sequences of several Clivia miniata mannose-binding lectingenes. A vitamin-binding protein may also be used, such as avidin. SeePCT application US93/06487, the contents of which are herebyincorporated by reference. This application teaches the use of avidinand avidin homologues as larvicides against insect pests.

Yet another insect resistance gene is an enzyme inhibitor, for example,a protease or proteinase inhibitor or an amylase inhibitor. See, forexample, Abe et al., (1987) (nucleotide sequence of rice cysteineproteinase inhibitor), Huub et al., (1993) (nucleotide sequence of cDNAencoding tobacco proteinase inhibitor I), and Sumitani et al., (1993)(nucleotide sequence of Streptomyces nitrosporeus α-amylase inhibitor).An insect-specific hormone or pheromone may also be used. See, forexample, Hammock et al., (1990) disclosing baculovirus expression ofcloned juvenile hormone esterase, an inactivator of juvenile hormone.

Still other examples include an insect-specific antibody or animmunotoxin derived therefrom and a developmental-arrestive protein. SeeTaylor et al., (1994), who described enzymatic inactivation intransgenic tobacco via production of single-chain antibody fragments.

E. Modified Fatty Acid, Phytate and Carbohydrate Metabolism

Genes may be used conferring modified fatty acid metabolism. Forexample, stearyl-ACP desaturase genes may be used. See Knutzon et al.,(1992). Various fatty acid desaturases have also been described, such asa Saccharomyces cerevisiae OLE1 gene encoding delta-9 fatty aciddesaturase, an enzyme which forms the monounsaturated palmitoleic (16:1)and oleic (18:1) fatty acids from palmitoyl (16:0) or stearoyl (18:0)CoA (McDonough et al., 1992); a gene encoding a stearoyl-acyl carrierprotein A9 desaturase from castor (Fox et al., 1993); Δ6 and Δ12desaturases from the cyanobacteria Synechocystis responsible for theconversion of linoleic acid (18:2) to gamma-linolenic acid (18:3 gamma)(Reddy et al., 1993); a gene from Arabidopsis thaliana that encodes anomega-3 desaturase (Arondel et al., 1992); plant Δ9 desaturases (PCTApplication Publ. No. WO 91/13972) and soybean and Brassica Δ15desaturases (European Patent Application Publ. No. EP 0616644).

Phytate metabolism may also be modified by introduction of aphytase-encoding gene to enhance breakdown of phytate, adding more freephosphate to the transformed plant. For example, see Van Hartingsveldtet al., (1993), for a disclosure of the nucleotide sequence of anAspergillus niger phytase gene. This, for example, could be accomplishedby cloning and then reintroducing DNA associated with the single allelewhich is responsible for mutants characterized by low levels of phyticacid. See Raboy et al., (1990).

A number of genes are known that may be used to alter carbohydratemetabolism. For example, plants may be transformed with a gene codingfor an enzyme that alters the branching pattern of starch. See Shirozaet al., (1988) (nucleotide sequence of Streptococcus mutantsfructosyltransferase gene), Steinmetz et al., (1985) (nucleotidesequence of Bacillus subtilis levansucrase gene), Pen et al., (1992)(production of transgenic plants that express Bacillus lichenifonnisα-amylase), Elliot et al., (1993) (nucleotide sequences of tomatoinvertase genes), Sergaard et al., (1993) (site-directed mutagenesis ofbarley α-amylase gene), and Fisher et al., (1993) (maize endospermstarch branching enzyme II). The Z10 gene encoding a 10 kD zein storageprotein from maize may also be used to alter the quantities of 10 kDZein in the cells relative to other components (Kirihara et al., 1988).

F. Improved Cotton Fiber Characteristics

Fiber characteristics such as fiber quality of quantity representanother example of a trait that may be modified in cotton varieties. Forexample, U.S. Pat. No. 6,472,588 describes transgenic cotton plantstransformed with a sucrose phosphate synthase nucleic acid to alterfiber characteristics such as strength, length, fiber fineness, fibermaturity ratio, immature fiber content, fiber uniformity, andmicronaire. Cotton plants comprising one or more genes coding for anenzyme selected from the group consisting of endoxyloglucan transferase,catalase and peroxidase for the improvement of cotton fibercharacteristics are also described in U.S. Pat. No. 6,563,022. Cottonmodification using ovary-tissue transcriptional factors preferentiallydirecting gene expression in ovary tissue, particularly in very earlyfruit development, utilized to express genes encoding isopentenyltransferase in cotton ovule tissue and modify the characteristics ofboll set in cotton plants and alter fiber quality characteristicsincluding fiber dimension and strength is discussed in U.S. Pat. No.6,329,570. A gene controlling the fiber formation mechanism in cottonplants is described in U.S. Pat. No. 6,169,174.

Genes involved in lignin biosynthesis are described by Dwivedi et al.,(1994); Tsai et al., (1995); U.S. Pat. No. 5,451,514 (claiming the useof cinnamyl alcohol dehydrogenase gene in an antisense orientation suchthat the endogenous plant cinnamyl alcohol dehydrogenase gene isinhibited).

III. TISSUE CULTURES AND IN VITRO REGENERATION OF COTTON PLANTS

A further aspect of the invention relates to tissue cultures of thecotton variety designated MX0623B2RF. As used herein, the term “tissueculture” indicates a composition comprising isolated cells of the sameor a different type or a collection of such cells organized into partsof a plant. Exemplary types of tissue cultures are protoplasts, calliand plant cells that are intact in plants or parts of plants, such asembryos, pollen, flowers, leaves, roots, root tips, anthers, and thelike. In a preferred embodiment, the tissue culture comprises embryos,protoplasts, meristematic cells, pollen, leaves or anthers.

An important ability of a tissue culture is the capability to regeneratefertile plants. This allows, for example, transformation of the tissueculture cells followed by regeneration of transgenic plants. Fortransformation to be efficient and successful, DNA must be introducedinto cells that give rise to plants or germ-line tissue.

Plants typically are regenerated via two distinct processes; shootmorphogenesis and somatic embryogenesis (Finer, 1996). Shootmorphogenesis is the process of shoot meristem organization anddevelopment. Shoots grow out from a source tissue and are excised androoted to obtain an intact plant. During somatic embryogenesis, anembryo (similar to the zygotic embryo), containing both shoot and rootaxes, is formed from somatic plant tissue. An intact plant rather than arooted shoot results from the germination of the somatic embryo.

Shoot morphogenesis and somatic embryogenesis are different processesand the specific route of regeneration is primarily dependent on theexplant source and media used for tissue culture manipulations. Whilethe systems are different, both systems show variety-specific responseswhere some lines are more responsive to tissue culture manipulationsthan others. A line that is highly responsive in shoot morphogenesis maynot generate many somatic embryos. Lines that produce large numbers ofembryos during an induction step may not give rise to rapidly-growingproliferative cultures. Therefore, it may be desired to optimize tissueculture conditions for each cotton line. These optimizations may readilybe carried out by one of skill in the art of tissue culture throughsmall-scale culture studies. In addition to line-specific responses,proliferative cultures can be observed with both shoot morphogenesis andsomatic embryogenesis. Proliferation is beneficial for both systems, asit allows a single, transformed cell to multiply to the point that itwill contribute to germ-line tissue.

Embryogenic cultures can also be used successfully for regeneration,including regeneration of transgenic plants, if the origin of theembryos is recognized and the biological limitations of proliferativeembryogenic cultures are understood. Biological limitations include thedifficulty in developing proliferative embryogenic cultures and reducedfertility problems (culture-induced variation) associated with plantsregenerated from long-term proliferative embryogenic cultures. Some ofthese problems are accentuated in prolonged cultures. The use of morerecently cultured cells may decrease or eliminate such problems.

IV. DEFINITIONS

In the description and tables herein, a number of terms are used. Inorder to provide a clear and consistent understanding of thespecification and claims, the following definitions are provided:

A: When used in conjunction with the word “comprising” or other openlanguage in the claims, the words “a” and “an” denote “one or more.”

Allele: Any of one or more alternative forms of a gene locus, all ofwhich alleles relate to one trait or characteristic. In a diploid cellor organism, the two alleles of a given gene occupy corresponding locion a pair of homologous chromosomes.

Backcrossing: A process in which a breeder repeatedly crosses hybridprogeny, for example a first generation hybrid (F₁), back to one of theparents of the hybrid progeny. Backcrossing can be used to introduce oneor more single locus conversions from one genetic background intoanother.

Crossing: The mating of two parent plants.

Cross-pollination: Fertilization by the union of two gametes fromdifferent plants.

Desired Agronomic Characteristics: Agronomic characteristics (which willvary from crop to crop and plant to plant) such as yield, maturity, pestresistance and lint percent which are desired in a commerciallyacceptable crop or plant. For example, improved agronomiccharacteristics for cotton include yield, maturity, fiber content andfiber qualities.

Diploid: A cell or organism having two sets of chromosomes.

Disease Resistance: The ability of plants to restrict the activities ofa specified pest, such as an insect, fungus, virus, or bacterial.

Disease Tolerance: The ability of plants to endure a specified pest(such as an insect, fungus, virus or bacteria) or an adverseenvironmental condition and still perform and produce in spite of thisdisorder.

Donor Parent: The parent of a variety which contains the gene or traitof interest which is desired to be introduced into a second variety.

ELS: The abbreviation for “Extra Long Staple.” ELS is the groupclassification for cotton in the longest staple length category. As usedin practice and for commerce, ELS denotes varieties belonging to thespecies G. barbadense that have superior fiber qualities, includingclassification in the longest staple length category.

Emasculate: The removal of plant male sex organs or the inactivation ofthe organs with a cytoplasmic or nuclear genetic factor conferring malesterility or a chemical agent.

Essentially all the physiological and morphological characteristics: Aplant having essentially all the physiological and morphologicalcharacteristics means a plant having the physiological and morphologicalcharacteristics, except for the characteristics derived from the desiredtrait.

F₁ Hybrid: The first generation progeny of the cross of two nonisogenicplants.

Fallout (Fo): As used herein, the term “fallout” refers to the rating ofhow much cotton has fallen on the ground at harvest.

2.5% Fiber Span Length: Refers to the longest 2.5% of a bundle of fibersexpressed in inches as measured by a digital fibergraph.

Fiber Characteristics: Refers to fiber qualities such as strength, fiberlength, micronaire, fiber elongation, uniformity of fiber and amount offiber.

Fiber Elongation: Sometimes referred to as E1, refers to the elongationof the fiber at the point of breakage in the strength determination asmeasured by High Volume Instrumentation (HVI).

2.5% Fiber Span Length: Refers to the longest 2.5% of a bundle of fibersexpressed in inches as measured by a digital fibergraph.

Fiber Span Length: The distance spanned by a specific percentage offibers in a test specimen, where the initial starting point of thescanning in the test is considered 100 percent as measured by a digitalfibergraph.

Fiber Strength: Also referred to as T1, denotes the force required tobreak a bundle of fibers. Fiber strength is expressed in millinewtons(mn) per tex on a stelometer.

Fruiting Nodes: The number of nodes on the main stem from which arisebranches that bear fruit or boll in the first position.

Genotype: The genetic constitution of a cell or organism.

Gin Turnout: Refers to fraction of lint in a machine harvested sample ofseed cotton (lint, seed, and trash).

Haploid: A cell or organism having one set of the two sets ofchromosomes in a diploid.

Linkage: A phenomenon wherein alleles on the same chromosome tend tosegregate together more often than expected by chance if theirtransmission was independent.

Lint Index: The weight of lint per seed in milligrams.

Lint Percent: Refers to the lint (fiber) fraction of seed cotton (lintand seed).

Lint Yield: Refers to the measure of the quantity of fiber produced on agiven unit of land. Presented below in pounds of lint per acre.

Lint/boll: As used herein, the term “lint/boll” is the weight of lintper boll.

Maturity Rating: A visual rating near harvest on the amount of openboils on the plant. The rating range is from 1 to 5, 1 being early and 5being late.

Micronaire: A measure of the fineness of the fiber. Within a cottoncultivar, micronaire is also a measure of maturity. Micronairedifferences are governed by changes in perimeter or in cell wallthickness, or by changes in both. Within a variety, cotton perimeter isfairly consistent and maturity will cause a change in micronaire.Consequently, micronaire has a high correlation with maturity within avariety of cotton. Maturity is the degree of development of cell wallthickness. Micronaire may not have a good correlation with maturitybetween varieties of cotton having different fiber perimeter. Micronairevalues range from about 2.0 to 6.0:

Phenotype: The detectable characteristics of a cell or organism, whichcharacteristics are the manifestation of gene expression.

Plant Height: The average height in meters of a group of plants.

Quantitative Trait Loci (QTL): Quantitative trait loci (QTL) refer togenetic loci that control to some degree numerically representabletraits that are usually continuously distributed.

Recurrent Parent: The repeating parent (variety) in a backcross breedingprogram. The recurrent parent is the variety into which a gene or traitis desired to be introduced.

Regeneration: The development of a plant from tissue culture.

Seed/boll: Refers to the number of seeds per boll.

Seedcotton/boll: Refers to the weight of seedcotton per boll.

Seedweight: Refers to the weight of 100 seeds in grams.

Self-pollination: The transfer of pollen from the anther to the stigmaof the same plant or a plant of the same genotype.

Single Locus Converted (Conversion) Plant: Plants which are developed bya plant breeding technique called backcrossing wherein essentially allof the desired morphological and physiological characteristics of avariety are recovered in addition to the characteristics conferred bythe single locus transferred into the variety via the backcrossingtechnique. A single locus may comprise one gene, or in the case oftransgenic plants, one or more transgenes integrated into the hostgenome at a single site (locus).

Stringout Rating: also sometimes referred to as “Storm Resistance”refers to a visual rating prior to harvest of the relative looseness ofthe seed cotton held in the boll structure on the plant. The ratingvalues are from 1 to 5 (tight to loose in the boll).

Substantially Equivalent: A characteristic that, when compared, does notshow a statistically significant difference (e.g., p=0.05) from themean.

Tissue Culture: A composition comprising isolated cells of the same or adifferent type or a collection of such cells organized into parts of aplant.

Transgene: A genetic locus comprising a sequence which has beenintroduced into the genome of a cotton plant by transformation.

Uniformity Ratio: A measure of the relative fiber span length uniformityof a bundle of fibers. The uniformity ratio is determined by dividingthe 50% fiber span length by the 2.5% fiber span length.

Vegetative Nodes: The number of nodes from the cotyledonary node to thefirst fruiting branch on the main stem of the plant.

V. DEPOSIT INFORMATION

Applicant has deposited at least 2500 seeds of cotton variety MX0623B2RFdisclosed herein with the American Type Culture Collection (ATCC), 10801University Boulevard, Manassas, Va. 20110-2209 USA. The accession numberfor the deposit is ATCC Accession No. PTA-9483 and the date of depositis Sep. 10, 2008. Access to this deposit will be available during thependency of the application to the Commissioner of Patents andTrademarks and persons determined by the Commissioner to be entitledthereto upon request. The deposit will be maintained for a period of 30years, or 5 years after the most recent request, or for the enforceablelife of the patent, whichever is longer, and will be replaced if itbecomes nonviable during that period. Applicant does not waive anyinfringement of rights granted under this patent or under the PlantVariety Protection Act (7 U.S.C. 2321 et seq.).

REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference.

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1. A cell comprising at least a first set of chromosomes of cottonvariety MX0623B2RF, wherein a sample of seed of said variety has beendeposited under ATCC Accession No. PTA-9483.
 2. The cell of claim 1,wherein the cell is a cell of cotton variety MX0623B2RF, wherein asample of seed of said variety has been deposited under ATCC AccessionNo. PTA-9483.
 3. A plant of cotton variety MX0623B2RF, wherein a sampleof seed of said variety has been deposited under ATCC Accession No.PTA-9483.
 4. A plant part of the plant of claim 3, wherein the plantpart comprises a cell of cotton variety MX0623B2RF.
 5. The plant part ofclaim 3, further defined as pollen, meristem or an ovule.
 6. A tissueculture of regenerable cells according to claim
 2. 7. A seed of cottonvariety MX0623B2RF, wherein the seed comprises cells according to claim2.
 8. A cotton plant regenerated from the tissue culture of claim 6,wherein the regenerated cotton plant expresses all of the physiologicaland morphological characteristics of cotton variety MX0623B2RF, whereina sample of seed of said variety has been deposited under ATCC AccessionNo. PTA-9483.
 9. A method of producing cotton seed, comprising crossingthe plant of claim 3 with itself or a second cotton plant.
 10. Themethod of claim 9, defined as comprising crossing the plant of cottonvariety MX0623B2RF with a second, distinct cotton plant.
 11. An F₁hybrid cotton seed produced by the method of claim
 10. 12. An F₁ hybridcotton plant produced by growing the seed of claim
 11. 13. A method ofproducing a cotton plant comprising an added desired trait, the methodcomprising introducing a transgene conferring the desired trait into thecotton plant of claim
 3. 14. The method of claim 13, wherein the desiredtrait is selected from the group consisting of male sterility, herbicidetolerance, insect or pest resistance, disease resistance, modified fattyacid metabolism, modified carbohydrate metabolism and modified cottonfiber characteristics.
 15. The method of claim 14, wherein the desiredtrait is herbicide tolerance and the tolerance is conferred to anherbicide selected from the group consisting of glyphosate,sulfonylurea, imidazalinone, dicamba, glufosinate, phenoxy proprionicacid, cyclohexanedione, triazine, benzonitrile and broxynil.
 16. Themethod of claim 13, wherein the desired trait is insect resistance andthe transgene encodes a Bacillus thuringiensis (Bt) endotoxin.
 17. Aplant produced by the method of claim 13, wherein the plant comprisesthe desired trait and otherwise comprises all of the physiological andmorphological characteristics of cotton variety MX0623B2RF when grown inthe same environmental conditions, wherein a sample of seed of saidvariety has been deposited under ATCC Accession No. PTA-9483.
 18. Amethod of introducing a single locus conversion into cotton varietyMX0623B2RF comprising: (a) crossing a plant of variety MX0623B2RF,wherein a sample of seed of said variety has been deposited under ATCCAccession No. PTA-9483, with a second plant to produce cotton seed,wherein the second plant comprises a desired single locus; (b) growingF1 progeny plants from the seed and selecting at least a first a firstF1 progeny plant that has the single locus to produce selected F1progeny plants; (c) crossing the selected progeny plants with at least afirst plant of variety MX0623B2RF to produce backcross progeny plants;(d) selecting backcross progeny plants that have the single locus andphysiological and morphological characteristics of cotton varietyMX0623B2RF to produce selected backcross progeny plants; and (e)repeating steps (c) and (d) one or more times in succession to produceselected second or higher backcross progeny plants that comprise thesingle locus and otherwise comprise all of the physiological andmorphological characteristics of cotton variety MX0623B2RF when grown inthe same environmental conditions.
 19. The method of claim 18, whereinthe single locus confers a trait selected from the group consisting ofmale sterility; herbicide tolerance; insect or pest resistance; diseaseresistance; modified fatty acid metabolism; modified carbohydratemetabolism; and modified cotton fiber characteristics.
 20. The method ofclaim 19, wherein the trait is tolerance to an herbicide selected fromthe group consisting of glyphosate, sulfonylurea, imidazalinone,dicamba, glufosinate, phenoxy proprionic acid, cyclohexanedione,triazine, benzonitrile and broxynil.
 21. The method of claim 19, whereinthe trait is insect resistance and the insect resistance is conferred bya transgene encoding a Bacillus thuringiensis endotoxin.
 22. A cottonplant produced by introducing a single locus conversion into cottonvariety MX0623B2RF, or a selfed progeny thereof, wherein a sample ofseed of said variety has been deposited under ATCC Accession No.PTA-9483, wherein the single locus conversion was introduced into cottonvariety MX0623B2RF by backcrossing or genetic transformation.
 23. Amethod of producing an inbred cotton plant derived from the cottonvariety MX0623B2RF, the method comprising the steps of: (a) obtainingcotton seed by crossing a plant of cotton variety MX0623B2RF with asecond plant, wherein a sample of seed of said variety has beendeposited under ATCC Accession No. PTA-9483 and growing at least a firstseed to produce a progeny plant; (b) crossing the progeny plant withitself or a second plant to produce a seed of a progeny plant of asubsequent generation; (c) growing a progeny plant of a subsequentgeneration from said seed and crossing the progeny plant of a subsequentgeneration with itself or a second plant; and (d) repeating steps (b)and (c) for an additional 3-10 generations with sufficient inbreeding toproduce an inbred cotton plant derived from the cotton varietyMX0623B2RF, wherein a sample of seed of said variety has been depositedunder ATCC Accession No. PTA-9483.
 24. A commodity plant productcomprising at least a first cell according to claim
 1. 25. The commodityplant product of claim 24, wherein the commodity plant product is acotton boll or cotton seed oil.